In-flight oxidation of composite powder particles during thermal spraying

This paper presents a mathematical model of the in-flight thermal behavior and oxidation of powder particles during thermal spray deposition. In parti cular, stainless steel and Cr3C2-NiCr particles are investigated. The in-fl ight model accounts for the acceleration and deceleration of the particles during flight under variable fluid velocity, while the thermal model takes into account heating, melting, cooling and possible solidification as the p article travels towards the substrate. A finite difference method is used t o solve the thermal energy conservation equation of the particles. The mode l includes non-equilibrium calculations of the phase change phenomena in th e liquid-solid (mushy) zone and dissolution of the ceramic reinforcement in the composite particles. The growth of the oxide layer at the particle sur face is represented by a modified boundary condition, which includes finite -rate oxidation. The results obtained give the interrelations between vario us process parameters and the oxidation phenomenon. (C) 2001 Elsevier Scien ce Ltd. All rights reserved.